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strfry

The most efficient Nostr relay. High-performance C++ implementation using LMDB.

Overview​

strfry is designed for large-scale public relays. Written in C++, it offers exceptional performance while maintaining low resource usage — it even runs great on a Raspberry Pi 5.

Key Features​

Performance​

  • LMDB storage — Memory-mapped database for fast reads
  • Low memory footprint — Efficient even on constrained hardware
  • High throughput — Handles thousands of concurrent connections

Negentropy Sync​

strfry's most distinctive feature is set reconciliation using the Negentropy protocol:

┌─────────────┐                    ┌─────────────┐
│   Relay A   │                    │   Relay B   │
│             │                    │             │
│  Events:    │   Negentropy       │  Events:    │
│  {1,2,3,5}  │◄──────────────────►│  {1,2,4,5}  │
│             │   Sync Protocol    │             │
└─────────────┘                    └─────────────┘
              │                    │
              │  Only transfer     │
              │  missing events    │
              │  (3 → B, 4 → A)    │
              └────────────────────┘

Benefits:

  • Bandwidth efficient — Only transfers differences
  • Works with filters — Sync arbitrary nostr filter results
  • Relay-to-relay — Synchronize relays efficiently
  • Client sync — Clients can use it too

Event Compression​

# Compress events using zstd dictionaries
strfry dict --compress ./events.json

# Events remain efficiently queryable
# Only raw JSON is compressed, not indices

Stream Router​

Handle multiple relay streams in one process:

strfry router --config router.conf

Features:

  • Pre-filter events with nostr filters
  • Plugin support for custom logic
  • Efficient multi-stream handling

Installation​

From Source​

git clone https://github.com/hoytech/strfry.git
cd strfry
git submodule update --init
make setup-golpe
make -j4

./strfry relay

Docker​

docker run -p 7777:7777 -v ./strfry-data:/app/strfry-db \
  dockurr/strfry

Configuration​

# strfry.conf

relay:
  bind: 0.0.0.0
  port: 7777

  info:
    name: "My Relay"
    description: "A strfry relay"
    contact: "admin@example.com"

  # Performance tuning
  maxWebsocketPayloadSize: 131072
  autoPingSeconds: 30
  enableTcpKeepalive: true

  # Query limits
  queryTimesliceBudgetMicroseconds: 5000
  maxFilterLimit: 1000
  maxSubsPerConnection: 50

  # Write policy
  writePolicy:
    plugin: ""  # Optional plugin for custom logic

Plugins​

strfry supports plugins for custom event processing:

#!/bin/bash
# write-policy.sh - Accept only kind 1 events

read event
kind=$(echo "$event" | jq -r '.event.kind')

if [ "$kind" = "1" ]; then
  echo '{"action":"accept"}'
else
  echo '{"action":"reject","msg":"only kind 1 allowed"}'
fi

Configure in strfry.conf:

writePolicy:
  plugin: "./write-policy.sh"

Commands​

# Start relay
strfry relay

# Export events
strfry export > events.jsonl

# Import events
strfry import < events.jsonl

# Sync with another relay
strfry sync wss://other-relay.example

# Compress events
strfry dict --compress

# Stream router
strfry router --config router.conf

Performance Tuning​

For High Traffic​

# Increase connection limits
maxSubsPerConnection: 100
maxFilterLimit: 5000

# Tune query budget
queryTimesliceBudgetMicroseconds: 10000

For Low Memory​

# Reduce buffer sizes
maxWebsocketPayloadSize: 65536

# Lower connection limits
maxSubsPerConnection: 20

Comparison​

Featurestrfrynostreamrnostr
LanguageC++TypeScriptRust
StorageLMDBPostgreSQLVarious
NegentropyYesNoNo
MemoryLowMediumLow
Best forLarge publicEasy setupPerformance

See Also​